Synthesis and characterization of stable betainic pyrimidinaminides

Abstract

Depending on electronically or kinetically stabilizing effects determined by the substitution pattern or the reaction conditions, 6‐amino substituted (5‐chloropyrimidine‐2,4‐diyl)bis(hetarenium) salts or 5‐chloro‐2,6‐bis‐(pyridinio)‐pyrimidin‐4‐aminides are formed on nucleophilic substitution of 4‐(dimethylamino)pyridine, 4‐(pyrrolidin‐1‐yl)pyridine, or 1‐methylimidazole on 4‐amino substituted 2,5,6‐trichloropyrimidines.

Synthesis of a Pyrazol-3-ylidene Palladium Complex, Pyrazolium Salts and Mesomeric Betaines of Pyrazole as N-Heterocyclic Carbene Precursors

“…The ligand donor strength of pyrazol-3-ylidene and pyrazol-4-ylidene has been determined by 13 C NMR spectroscopy [32]. In continuation of our studies of heterocylic mesomeric betaines [33,34], zwitterions [35,36], N-heterocyclic carbenes [37 -39], and the chemistry of organic polycations [40], we describe here the synthesis of a new pyrazol-3-ylidene palladium complex, as well as new aspects of the syntheses and properties of pyrazolium salts and pyrazolium-3-and -4-carboxylates as potential N-heterocyclic carbene precursors.…”

Borane adducts of punicine and of its dehydroxy derivatives (pyridinium-1-yl)-2- and 3-phenolates

“…[10][11][12][13] Thus punicine proved to be a suitable model compound to study the different types of conjugation which are known to govern the chemical behaviour of mesomeric betaines considerably. [14][15][16][17] In continuation of our interest in punicines and pyridinium salts [18][19][20] we report here on the synthesis of the tris(pentafluorophenyl)borates of punicine and of its derivatives which strongly depends on the position of the olate group in the mesomeric betaine which determine its type of conjugation.…”

Synthesis of Tetraoxygenated Terephthalates via a Dichloroquinone Route: Characterization of Cross‐Conjugated Liebermann Betaine Intermediates

“…Mesomeric, heterocyclic betaines possess intriguing electronic structures that present challenges to theories of electronic structure and systems of classification alike [7][8]. They serve as intermediates in the synthesis of aromatic and heterocyclic compounds,[7][9] and some have been isolated from natural sources [10] . Liebermann and Lisser had reported the single representative 4b in 1934 and assigned its structure based on indirect arguments [6][11].…”